Controllable pitch propeller



April 24, 195i H. CARSON vET AL .CONTROLLABLE mea PROPELLER Filed Nov. 11, 1944 H. CARSON ET AL.

CONTROLLABLE PITCI-I PROPELLER April 24, 1951 m5 Raw T wdM. ma.; www H/u 4 Sheets-Sheet 2 Filed Nov. ll, 1944 70 ,00 yf Q4 @ATTORNEYS April 24, 195i H. CARSON ET A1. 2,550,529

CONTROLLABLE FITCH PROPELLER FledNOv. 11, 1944 4 Sheets-Sheet 5 lNVENTORS Hayward Cdr507z BY Fzcha rd E. Moore gl Z l ATTORNEYS April 24, 1951 H. CARSON ET AL 2,550,529

CONTROLLABLE FITCH PROPELLER Filed Nov. 11, 1944 4 sheets-sheet 4 atented pr. 24, igt-'51 CoNTRoLLABLE PITCHPROPELLER Howard Cars-on and Richard E.M'oore, Dayton,

Ohio,v assignorsto Gene ral Motors Corporation,

Y Detroit, Mich., a corporation .of Delaware ApplieationNovemberii, 1944,serial Nac. atasco l 'This' invention relates to a variable pressure hydraulic system for the control of pitch of pro` peller blades in van aircraft propeller.

The principal object of the invention is to provide a'system and Vmechanism inw-nich a pumpor pressure creating means operates v-toproduce-a pressure andis controlled'tby the pressure 'nece esa-ry to maintain the system in equilibrium, 'and to actua-ily causean operative change when cal-'led upon. I

Another object of the invention is to provide a hydraulic system and mechanism` that will oper'd ate to provide at all times a Amaterial excess of iluid-=pressure for operating under all'conditions required.

Another object of the invention is to provide a Vfluid pressure control system inw-nich a "po- Y tential of low pressure is supplied `for normal' propeller operation, and in `which al Ava-riabl'y higher pressure is available for-effecting control where the conditions demander indicate that a force higherthan normal is yrequired orde-V sirable.

. the control functions depending Aupon 4the `demand of relementsor units to be controlled.

Further objects and'advantages of'the'present invention -will be apparent from the 'following descripti0n,referenee being' had 'to `the vaccompanying drawingsv wherein al preferred embodiment of the presentinvention is clearly shown.

In the drawings:-

`ligil is a curve showing the-'needs offluidl pressure for v accomplishing pitch control changes Ain one type of propeller.

Fig'. 2 is a three dimensional curve giving the values of pressures at'the governor distributing ports of a governor `unit in one type ofpropel'ler.

Fig. 3 `to Fig. Ginclusive showalternate'methods of accomplishing variable 4pressure control in a governing system.. In Fig. v3,1.the variable pressure control,V is applied 'to .one controlrpas.- sage only of the system, while Fig'. Lifappliesthe variable pressure :control togbothscontrol fpase.. sages. In Figs. 5 and 6, the pressure controlfsystern applies theincreased 'control force by sub-V stantial increments of pressuregFig. t applying the force from one controlled passage, whilejirig. 5 is dual operating in that it applies `the added pressurefrom either one of two controlled. ,pafs- Sages.

Figs; to i3 .are structin'al views showing the ieaturesiof the method of Fig. 3 embodied in an existing and 'currently operated aircraft propelsectional view through the regulator unit after the cover 'member has been removed, substantially as indicated by the:-

linesanci arrows fii-iiof Fig. 7.

FigqQ is ari-enlarged sectiona'lriew through the Vregulator Asubstantially as indicated "byv the lines and arrows 9-9 of Fig. 8.

Fig. i0 is aiong-itudinal `section through one type of 'pressurereguiator"valve 'embodied-inthe systerny'it being aiview 'substantially as indicated bythe lines and arrows lli'or Fig. 8. Fig llis a similar sectional view, on-an en= larged scale; of a modified'fornofthevalving portion ofjthe control valve.

Fig.' i2 is airagmentary unit substantially 4as shown Fig. l1.

Fig. is is anend view by the line `and arrows A variable pressure plied to thefc'ontrol ofl may be donned vasY oney in which, the v-pressul'reat ieg-is of nig..- 11.

which: the pumpope'rates fis .controlledby `the pressurenecessaryiforemai taining thesysternin equilibrium-orion actually causing operation ofy propeller control mechanism.

As the force'stobe-overcome in prop'elflerconA trol, very little the condition-- where fveryhigh pressure e is-reY be seen is obtained if` purnpat all times at the maximum lpressurerequired under extreme at 1 the centrifugal. effector the pressure control valvein :order .to establish. that the a constant pres` of apropeller 'mechasideviewof the valve i by the arrow AIii `oiof the same as--indicated hydraulic system as apf a 'constant speed propeller l change. from the condition Vunder which pressureis required for .operatioifn` to that a distinct sifivantageV i itis .not 'necessary to.4 operate 'the conditions. In the-present' typeL of .propellermusing a-constaiit pressurelhy-' I draulicsystem thefsys'tem operates continuously maximum pressureeveirequired aridis -1 relieved only slightly at lowervspeeds due tof/theare inefficient and can be improved upon, information on pressure required for operation of one type of propeller under different ight conditions is presented in Figure 1. The curves of this ligure show the pressures required to increase pitch for the flight condition of windmilling in a dive at 400 M. P. H., level flight with power on, take-off and ground running, respectively. The pressures all increase with rotational speed of the propeller as shown.

From Figure 1, it can be seen that high pressure is only required for unusual flight conditions under which the propeller will be operating for only a small fraction of the total time. It is dicult to set an safely be estimated that 90 percent of the operation of the propeller will be in the pressure region below 1200 p. s. i., as indicated by the dotted line of Figure 1.

It can, therefore, be seen that control of the propeller under normal conditions of operation can be accomplished with a pressure only slightly greater than one-half of the pressure that must be provided under the worst condition of operation (windmilling at high airspeed and maximum R. P. M.).

With a constant pressure system, the pump operates at a substantially constant pressure, and the governor throttles or reduces this pressure to the amount required for operation under the particular condition of flight. The pressure at which the pump operates may be controlled by the setting of a pressure control valve. This setting must besuch as to provide the maximum pressure that will ever be required for operation of the propeller. Except for operating conditions which involve very rapid rates of pitch change, where the propeller blades are moving at the same rate as the pump output, this maximum pressure will be maintained in the system.

With the variable pressure system shown schematically in Figure 3, the pump pressure is controlled by the requirements of operation as indicated by the governor. As can be seen from Figure 3, the principal diierence between the variable pressure system and a constant pressure system is the addition of a small secondary piston, As which is acted upon by the increased pitch pressureFPr of the system. The load resulting from the increase pitch pressure acting on the area of the secondary piston is applied to the bottom of the primary piston, Ap, in such a direction as to aid the spring Fs and centrifugal force For' tending to keep the valve closed.

By using a pressure control system as shown in Figure 3, it is possible to control the pump operating pressure and maintain this pressure at a certain ratio to the pressure lactually required to operate the propeller. With such a system the normal operating pressure will always be substantially lower than the maximum pressure required under the extreme flight condition of the propeller windmilling with the airplane in a high speed dive. As 'applied to the present constant pressure propellers, such a system would result in the pump operating below, for example, 500 p. s. i. instead of 1200 p. s. i. for all normal night conditions, and being raised to 1200 p. s. i. only when necessary to overcome the blade forces encountered in the Windmilling condition.

The lowering of the operating pressure for normal operation will result in less power input to the regulator unit and consequently less heat exact gure but it can 'with a'pump of given -pressure required to area As of the being generated through the dissipation of this power. Operation at lower pressure will also result in lower loads being imposed on the pump, control valves, seals, gaskets, etc., with resulting longer useful life of these parts. It has been found that close control of speed with a centrifugal governor becomes increasingly diicult as the operating pressure is increased. With the variable pressure system, governing for normal operation will be done at a reduced pressure and accurate speed control maintained as in the present constant pressure system.

'I'he use of such a system greatly simplifies the design of all the units comprising the control mechanism. It can be seen that in the case of the hydraulic pump, for example, that the design is simplied if operation at peak pressures is required for only short intervals. In general, overloading for short intervals is very possible design Where continuous operation at maximum pressure would result in wear and reduced life.

Methods of accomplishing pressure control Figures 3, 4, 5 andV 6 show alternate methods of accomplishing pressure control in a governing system. The system shown in Figure 3 appears at this time to be the Amost desirable for use in propellers with a variable pressure control for increase pitch only. The system shown in Figure 4 operates on the same principle as the system shown in Figure 3 with the additional advantage that it operates for both the increase and decrease pitch condition. In the present propeller designs it appears as though variable pressure control, or pressure loading, on decrease pitch is unnecessary, as the propeller blade forces tending to decrease pitch are sufficient to cause satisfactory operation.

The pressure control systems as shown in Figures 3 and 4 continuously control the pressure of the system under all conditions of operation. Those shown in Figures 5 and 6 are essentially two-pressure systems, where a distinct shift is made from one pump operating pressure to another at a predetermined value of the pressure required for operation of the system. These two-pressure systems as shown in Figures 5 and 6 are more complicated in construction than those shown in Figures 3 and 4, but are of value in systems where continuous control of pressure is undesirable or unnecessary.

As can be seen in Figure 3, this system operates on the principle that a measure of the overcome the forces acting in the system is obtained from Pr (increase pitch pressure) and used to control the pump pressure by means of applying this pressure to the pressure control valve. With this system, then, the higher the pressure Pr, the higher the pump pressure will be since the force determined by the pressure P1 and the area As acts to aid the spring and centrifugal forces tending to hold the valve closed.

With a view to knowing the pressures acting in the system under all conditions of operation, the following anaylsis may be carried out, with reference to Figure 3 where the symbols represented are dened as:

Pp=pump pressure-p. s. i'.

P1=increase pitch pressure-p. s. i.

Pn=decrease pitch pressure-p. s. i.

Ap=area of primary pressure control valve piston-ins.2

when the' pressures in passages 86 and 88 are the same.

In Fig. 6 the arrangement is much the same as in Fig. 3, except that a lockout valve 80 is inserted in the connection between the secondary piston chamber 60 and its fluid connection 62 with the increase pitch control port. The lockout valve 90 slides in a bore or cylinder 92 against a spring 94 in an extension 95 relieved to the outside at 96 to communicate with an axial passage 98 `leading to an annular groove |00. Here, the spring 94 normally closes the communication between Ythe chamber 60 and the passage 62, but

is operable when the pressure in the control passage is applied with suicient force against the part ,90 to open such communication.

In Fig. 5 the pressure control valve is dispensed with insofar as the described structure is concerned, and is replaced by a high pressure relief valve |02 in therline I4 at the outlet of the pump, While an extension of the pump pressure line I4- is made at |62 to a low pressure relief valve |06. Across the extent of this line |04 there is a double acting selector or lock-out valve |08 having opposed heads II and H2 joined by a stem of reduced section that normally permits fluid passage along the line 04. However the heads IIO and II2 are exposed to the pressure at the control ports 22, 24 and 28, 30 respectively by passages I I4 and I I6 connected with chambers II8, |20 in which are housed springs |22 and apertured discs |24, the springs and discs normally keeping the heads H6, II2 equally spaced for flow through the line |64. Upon application of fluid pressure at either of the control ports, that pressure is also applicable through the passages II4 or H6 as the case may be to push the head I I or I I2 to an intercepting relation across the line |04. When that is done the low pressure relief valve |66 is non operative and the control force is limited only by the setting of the high pressure relief valve |02.

Tracing the related actions and specific operation of the elements shown in Fig. 3, should be sufcient to illustrate the operation of the forms of invention shown in Figs. 4, and 6 as well. It is to beY understood of course that the valve units I8 and 50 are so mounted on the propeller mechanism that centrifugal force will be applied to the elements 34 and 62 tending tomove them radially outward from the axis of rotation, as will later appear from the description with respect to Fig. 8. As shown in Fig. 3, centrifugal force acts upon the elements 34 and 64 towards the top of the sheet. With respect to the governor valve I8, the plunger 34 is articulated to the lever 42 that is constantly urged radially inward by the spring 46 tending to rock the lever over the fulcrum 44, thereby opposing the centrifugalrforce acting upon the valve plunger. Movement of the fulcrum i4 along the lever 42 determines the relation ofcentrifugal and spring forces acting upon the plunger and its connected lever. When those `forces are in equilibrium the lands 36 and 38 will cover the control ports 22, 24 and 28, Si] substantially as shown in Fig. 3, and the propeller will be operating on speed. If the force of the spring 46 dominates, then the valve plunger 36 will occupy a position radially inward (downward) of that shown, and the propeller will be operating at underspeed If the centrifugal force acting upon the plunger and lever dominates, then the valve plunger 36 will occupy a position radially outward (upward) of that shown, and the propeller will be operating peller shaft |32 at overspeed The valve plunger 34 in moving along the bore of the porting sleeve 20 from its equilibrium position shown in Fig. 3 operates to v connect either set of control ports with the pressure input port I6, so that the devices attached to either of the passages 26 or 32 will then be exposed to whatever pressure that is existent in the line I4.

The potential of the pressure existent in passage I4 is determined by the variable pressure control valve 50. Centrifugal force acting upon the plunger 64 of that valve is assisted by the force of the spring 66, which both tend to move the plunger radially outward (upward) so that the portion 12 closes off the ports 56 exhausting back to the pump intake. The chamber 52 of the valve is always open to the pressure potential from the pump I0 which pressure is applied downwardly to the area of the head 12 in opposition to the spring and centrifugal force. With. the control ports of the governor valve I8 closed there is insuicient flow from the system to deplete the pressure of the pump that is being built up, and the component of pressure force applied to the area of 12 soon overcomes the combined spring and centrifugal forces, and the plunger 64 moves radially inward to uncover the outlets 56, which limits the pressure in the line I4 to a relatively low value for equilibrium conditions of the governor valve I8. The head 12 opens more or less the ports 56 as the pressure in the chamber 52 and line I4 rises or falls, but always maintains a sulicient head in the bore of porting sleeve 20 for application to the control ports upon movement of the plunger 34. When the valve 34 moves downward during an underspeed condition the pressure in I4 and the bore of sleeve 20 is applied to control ports 28, 36 for ow along control passage 32. Thatl flow momentarily reduces the pressure in I 4 and consequently 52 which relieves some of the pressure applied to the end area of 12, resulting in a radially outward movement of the plunger 64 to at least partially cut off the outlet at 56. Thus the pressure in I 4 is immediately raised to meet the needs of force application through the control passage 32.

When the plunger 34 moves radially outward (upward) during an overspeed condition the pressure in I4 and the bore of sleeve 20 is applied to control ports 22, 24 for flow along the control passage 26. The momentary reduction by reason of iiow is immediately reflected to the area of the head 12 and acts in a similar manner as just described to raise the pressure to be applied. That pressure to be applied in this instance is also increased through a further control effected by the valve unit 50. Coincident with directing pressure in I4 and 26 to the control passage 26 it is also applied to the fluid connection 62 which leads to the underside of secondary piston 14 aiding the centrifugal and spring force moving plunger 64 radially outward. Any outwardly directed force upon the plunger 64 tends to raise the blow off point at which the pressure in 52 will exhaust through 56. In this way the pressure within the pressure source line feeding into the governor valve I8 is raised or lowered to nt the needs for power required at the ends of the passages 26 and 32.

A physical embodiment of the features outlined by Fig. 3 is illustrated in Figs. 7 to 13 inclusive, in which |30 indicates an engine nosing or gear casing from which extends an engine driven prodrivably mounting a propeller f- 9 jl'iubr |"3 4*' by r means of, the: usual splines "and'nut f v| 36.' Thehubprovides a" pluralityof blade'sock- M=fets= |38 Within""vvhichare` joinnalled'"for` pitch shifting movementblades |40 'due to thet'bearings V442 andV nutI |44. Each*bladefenoloses in'its hollow root al hydraulic torque'unit `|46xcomprisingv a *cylinder |48 mounted `on* a blade driving Igear |58which"*hasrotatable driving'rel'ation Uwith" the blade |40. i The cylinder 48..'en'clo'ses a piston |52 that Ledivides the cylinder into twoiopposed chambers |54 and |56 eachconnectedvvith one ofthe pressure controlled passages-"26er 32 hereinbefore mentioned. "ins-'shown' the cham- "1 ber |56 is connectedL4 by a: fixed tube "I 58slidably extendingl throughithe piston '|52 with a--pas$2fge 7 |f60`that communicateswith the controlled'ipas- =sa'ge"`l 32 @at "1162; andY it, 'isfobviousf'that similar connection between" the chamber,`154`andfthe "fcontroll'ed' passagel ZB'may be; made'atifl. .""Irhe piston |52 has afv doubledgspline connectiongione f the interiore of "fthe cylinder' at "|661 andjthe other With-the exterior vof` affixed spindle" I||l"'at """|10. "f The" spindle |68v isffrigidly"mounted'ori 'the hub I 32= bymeans of a-` screvvy "device l |12'which "falsooperates`-fto'" secure* the i tube |68. Thus, rf2movementofthepiston 'I 52 axially cof'the cylinder 48 tvill effect Irotation of the cylinder :and consequentlyI rotation f'ofi the'blade A|40 depending wnfwhich fof theachambers'4154401s '|56 Ithe domiwnating fluid pressure-is fapplied-to.

@The application kof" fluid pressure lto 'onef side @1011 the other of 'f-thefipistori |52 is controlledby a `-;'regulator`"Ifllthat is mounted on an afttubular Miextension |16 offffthe-f nubi flv34. The regulator @comprises an annular-plate' |18; aecover |88 l`and fzfanfadapter assemblyf'|'82that=provide an lannular aled' *fchamber E184: constituting a reservoir' -Jfor ixistoring a quantity of'fluid pressure'medium'i and @housing the elementsfofthe contohmechanism.

.1a All `iof.` the vregulator Aexoepiffthe adapter assembly i'rotates fvvithfllthe: propeller," :while-'the 'latter r is ,restrainedtrffrom 'rotation fby vmeans V'of a lug and irmotch. 'engagement |186 ;vvithl axed part-of the supporting structure; such asfthe engine nosing ior ear casingrl 3|). P'Theaplate |118 irithisfforml is feast* to'embody tubes Iproviding'xtlfiel` passages-11| 4, 1- f26,'-32,1and A62 4vvith suche l'ateral'zop'enings as necessary to makezfluid "connection withi' thef fcontrol v .ndevices kor` units. nJuncturezfblocksscare:supplied flwhere desirable)-foromounting 'control 'units,=v and ifshouldfincludel rformounting Tof the x.governor fvalve unitt 8; 'andi F4190'` for; the;I mounting' Voffthe pressure control unit50.

One example isshown in Figi QfWhere-th'e block 4196 presents a -cupflike'f'recess 'rl-SZ-forfereception :of a'lter-:unitilfll threaded'ithereinfand having :Gentry notches-:|96 forgrlud coming'iinto the rei fcess'; fromI the" end lvof z l 4esupp-lying`fthe pump prese-isure. y A central drill-way? |98; leadsffromrthe interiorffof theY filter unit andi, communicatesvvitli the other= branch 'of ",thef passager 4 lleading to "the "Tfgovernor valve-- .unit 1| 8f] as i'shown' fin@ Fig :Si 8. ``i A afbranch 200 slantsradiallyYoutwardftofimakeicon- .nection with a -pumpsupply port i286 tothe'y presfasureucontrol va1ve-58,-wh-ile an additionalzpassage LA. :282- rma-kes;iu'nctureI with :1 the :secondary :piston Y f. fchamberq aand theep'assage62` connectingrtomthe pitch increase line 26.

The physical,.embodinfient; of v'the'.'pressure Icon- 5| fandthepassage '20|lof the`juncture `pad |98.

Thus; the'chamber '52 of the housing is always in @communication vvith the pressure" iluid atv pump lpressure".through4 the passage felements 206", *200, 188; |94,` |96 and I4. C'R'eferringfto' Figfljthat `10pressureisexiste'r'it on'one side of'the primary pistoni 'F2 and 'on both sides bf thelarge 4'diameter Ifhealf 68,-due to the damping aridi'equalizingfpassages" 21| 8 and 2-i 2 by-vvhicli" the fdamping'y cham- Joer 2 I4 is bled to fandy fromthe `chamber`52 'The valveunit'being-mounted onthe plate Illon a radiusl ofv rotationyand so 4that the headed Ve'nd f'is radially "outwardfthe centrifugal force 'ofirotation'lcp,` and the" force of the kvspringfiils;v'vill falvvay's vbein aiding relation, and the pump pressure'Pp applied to'thefprimary piston '12"froni the f "chamber""52 1 Will' be'the' "only joppos'ingf'f-orce. Vl-Domination of the pump pressure, When-exerted, moves" the primarypiston-radially inward against that 'cornbin'edY force. In`Fig. 10,' the primary 'l chamber/6l] areV each provided by a separate sleeve element'nestingWithintheb'ore of the'meinber forming' the main chambe'52. A spool'lke mem- 'l--ber VIii isaxially'bor'edto provid'the chamber "301` 54 "and" then enlarged to f receive a "sleeve 2"! 8 Vaxiprovding communication`VV with" the fo'utlet`56- .withe end oftthef chamber`52' 'by means of ailange AT228 received '-in a recess {ofa` cap'f230 attachedto vFtlfie housing'by sc'revvdevices232.` Thev cap 'also :retainsthefsle'eve"25| 8? in position vvithirifthesleeve 2`1| and'closes 'o'ithe end'of the secondarycham- .i f1ber.v Aseal ring 23 4 prevents leakage, aiid'@ cross wfsage vvth1i expanded opening" 242i houses ai' seal ng`f244', shown in'lig;` 9;adlopens`into the-pasage' 202 =exposed'tothefincreased `pitch`= pressure n through passage 62. Y

.Some modification bf ythe structureisshovvniin 5`ffFig'l11; Wherethe primary'piston chamber and "-,fthese'condary'piston'chamber are 4of substantially ffequal area. 'single'sleeve-like member `2f46f1has i asuc'cession 'of 'circumfere'nti'al grooves, in "alterhating ones of which starting from'the'chamb'er =60 52 *have* deposited Atherein seal "rings" 248'; 250 and fspe'ctivelyf opening" tobthe' central" bore of *the -flsl'e'eve which bore is"r'educ`ed"in diameterat'f`2'62 n.to slidably receiver 'and guide" anextension' 426 4 of ""theplunger 64. rin'al'end groove '266 is recep- 'ftive of a'yoke1v plate 3268 'which operates to secure trok-valve suitable.Y foniapplyingthe vari'ablepres-v1 70fthe"sleeve"24| in' position thrOli'ghr-the agency Gf sure according` to Figi;'BvisfshownfiriFigs'lO to T13 inclusive. :Wherenffpossible f-nthefz same freference .A :characters Vhave'.beentusedA to? illustrate fthe equi- @valent details loi'sstructurley; andt.:it":-therefore' ire- Vamains;onlyoogfdescribeyytl'ieparticularfidiierences.

" unit. The groov256communicates'through A21E! with 242 in the described manner, since the valve unit 59 is retained in proper alignedrelation with the respective ports by means of screw devices 212 threading into the body of the plate l 18.

Actuation of the pump I is eiected through the agency of a toothed spur 214 carried by the relatively xed adapter assembly |82, and thereby drives a pump pinion 216. The adapter assembly also provides a plurality of high lead screws 211 actuated by a toothed ring gear 21B oscillatable about the adapter assembly from a lever 23!! that effects longitudinal movement of a control ring 282 inside of the regulator. The control ring provides a groove 284 of wavy formation, and in which rides a shoe 286 supporting the fulcrumv 44 supporting the free end of the lever 42. The wavy formation of the groove eil'ects cyclic reciprocation of the valve 34 within its porting sleeve to eliminate static friction, While the lever and high lead screws provide for establishing basic control speeds. The cyclic reciprocation of the valve is but minute, or of such small extent as not to eiect an actual pitch change by the torque unit, but large enough to supply a succession of incrementally small impulses to one and then the other of the control ports. That assures that the control valve 34 will be kept shivering, so to speak, and conditioned to move to a controlling position with the least eiTort from a pitch shifting impulse.

Reverting to the operation of the pump, it will be constantly operated so long as the propeller is turning with respect to the eng-ine nosing casing |30 and the adapter assembly. By reason of the pressure control valve D, the output of the pump, or rather the potential of the pump delivery line I4 will be relatively low as regards the possibilities or capacity of the pump, because ight conditions, on the average, as shown by the curves of Fig. 1, necessitate but moderate controlling forces as compared with materially greater controlling forces during short intervals of propeller operation. The pressure control valve is so constituted that the pressure system will normally be charged with a suitable low potential pressure which is sufficient to operate the torque unit for a pitch decreasing function, but will immediately be increased to a suicient value for operating the torque unit for pitch increasing function. Thus, if a force greater than the average is required to effect working of the torque unit, the pressure system is charged with that greater force. The pressure control valve therefore controls the potential of the system in accordance with the demands of the work to be done by the torque units. The load upon the pump is thus materially reduced throughut the greater portion of its operation, and is loaded heavily only during irregular and short intervals of operation.

The advantages of operating the pump at pres-- s-ures lower than the maximum are many. Since normal operating pressures of a high pressure propeller will be no greater than the pressure at which the pump operates in the present production propeller, heat generation from the hydraulic-system will be no greater. Operating temperatures of the present production propeller are auxiliary means of cooling would have to be provided.

. 79 conduits, a pressure supply passage connecting pump driving gear,

or gear Another advantage of operating the pump at reduced pressure is that the load imposed on the bearings, seals, and the pump itself is greatly reduced for a large percentage of the total time of operation. Pumps, bearings, seals, etc., which are designed for continuous operation at 250G-3000 p. s. i. will last a lot longer if they are operated continuously at G-1500 p. s. i. and only required to withstand pressures of 2500,-3000 p. s. i. for shortv intervals of operation.

Accurate speed control is considerably easier with the pump operating at pressures below 1500 p. s. i. than it is above this pressure. With a high pump pressure it is necessary to have high pressure drops across the ports of the governor. With these high pressure drops, forces are set upon the governor piston due to the high velocity oil-bleed at the ports. These forces tend t0 unbalance the piston and the result is erratic speed control and chattering. The higher the operating pressures, the greater are these forces and themore di'iculty is encountered in obtaining accurate speed control. As all the flight conditions, where accurate speed control is necessary, are in the lower pressure region, it can be seen that more accurate speed control is possible with the variable pressure system.

It has been found that the above mentioned unbalancing forces on the governor piston can be greatly reduced with a positive overlap type of governor. This governor differs from the usual governor used on propellers up to this time, only in that a slight amount of positive overlap (.001- .003 inch) is maintained across each governor port. 'On the usual governor, a slight amount of negative overlap has been used in order to obtain a proportionalizing valve. It has been found. however,` that an extremely good proportionallzing valve can be made with a slight amount of positive overlap when the piston is kept jittering in the cylinder. This type of valve possesses the additional advantage that very little oil ow is passed through the ports when the propeller is in the on-speed condition. This reduction in oil flow aids in reducing the unbalanced forces and results in a more stable valve than can be obtained when negative overlap is used.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A propeller control mechanism of the chartuated means, a governor valve having control ports opening into said conduits mounted on the plate and responsive to the speed of rotation of the propeller for directing the application of said fluid pressure through one or the other of said the source of pressure with the governor valve, a pressure control valve carried Iby the plate opening into said pressure supply passage and including means for maintaining a predetermined pressure potential in said supply passage, and means :ramones 13 niort-2variablytinereasing:theipotentialwoi vpressure 'fin said supply passage in aocordanceswithrthe ".rwork to :besdone by Ltheffluid actuated ymeans-when connectedwwithl 'either .one of;- saidftuid pressure .1: conduits.

2; The combination setbforthrinfclaim 1L where- .v in. fthe pressure control .valvei.comprises` afspring lpressedfpiston earnanged-4 .to move radially -Lofpthe plate-to respond :to centrifugal; force saidrpiston having a primary area constantlyexposed .to-fthe.t

,i5-.1potentialnf--saidrpressure supply:passage and: a secondary area exposablethrough` avfeed-b'ack assagestoffthe potential: yof .f pressurewdirected v`tto ...s-one of the saidfluidpressure-conduits.

3.- fihe combination fset forth Yclaim 1w 'where .inethe pressure control" valve.- com-prises` avspring ..pressed piston frespondingftomentriiugal :fftrcerin `aiding .relationefand 'hav-ing: apri-mary. area. con- ."wstantly-lexposed to the potential offfsaid .pressure .-valve tothe pressurepotential-ottoneT-ofiithefrluictriz l....:pressure conduits.

4... The combination.-setzfortlrin claimfl-fwherethe. pressure Icontrol@valve comprises airspring jfs-pressed piston having. a primaryfarea =constantly -aexposed -to the --potentialfor said.: pressuref'supply passage for opposing saidtspring,..and a secondary a areaA with. rpassage .means-.connectin.g ijit=7 with:x a y.lpressure. .conduit iopposingf thefprimary :areal .and .exposable .,upon fdirectedapplications.: Suid .wpressureLto one i Vand..means...mounting., ythe pistone to move :radially Lof.. .the plate..to :respondio `,'centriiugal forces-in assisting` thespring.

y A. .propelleracontrol .mechanism of. lthe charjus-tablepropeller .havingahubzand a pluralfity'fof .blade fsockets with.. fluid actuated. .means f tornei lletting.` adjustment.of.;.the .pitch oir-'the bladesr-in aclfuof.tlie-.kade` sockets-comprising, alplate.ro f tating withthe hub, .pump .meansmounted @n.the. ,2 plate .and providing., a.fsource.of pressuref Huid.; a g. pair. of Lnuid. .pressure conduits on the plate rior ,.i '.supplyingldirected.fluid pressure.. to.- the. iu-idh-actuated'. Ineansra governor, .valve r.having...control ,ports.-..opening. into.said....conduits..rotatable-with- `ltheplate. and responsiveto :the speedwo rotation .l bf. said-.propeller .ior directing-.theA applicationpf 'said' pressure 'flu'id..t0.,one or. the .-.other,:.off.said A....conduits,. a. pressuresupply` .passageconnecting lthe source fofnpressure .with-.the lgouernormvalve, 1.Land aipressure, control. valve .carried ,by-tha plate .ifandhaving aprimaryarea.constantly exposed-to the potential of said.. pressure supply..` .passage '.tendingto .reducefthe .pressureiionmaintaining. a normal operating..pressure,. and having.. assecondary.- area. with, .passage .rneans:` connecting-...it v.y'vitha pressure. conduit in .opposedrelationto fthe. primary A.area .and .exposable .Atolthe .potential f either ,of ...said iluid ,pressurelconduitsl@upon 0direct'ed application of lfluid. .pressure :thereto 4ion increasing .the Ypotential .oi .pressureuiddirected 2 Lto'r the conduits in accordance.Witnltheldemands "of said fluid. actuated vmeans .wheneverv eithenfoi said pressure .conduits is connected. with .theeaid .f'source. A

f6.'A.prope1ler .control mechanism .of thechar- '.acterl .described for use withan hydraulically adjustable rotatable,- propeller..lfiavingH a...hub...and ".-"bl'ades, with .fl-uid actuated `nrieans .for adiustment blades, comprising. a. rotating.

ffregulator includingl meansfprovidingaisourcef'of g fpressureqfluid, afpair: of.` uid; pressure` conduits for supplying cli-rectediiuid .pressure .to :the fluid actuatedmeans, a-governorvalve having control 5l `ports i opening into.-said-conduitsresponsive-to c the jspeed of rotation of said propeller forf'direct- 4ing said pressure. fluid .to` oneor the other of said conduits, pressure controlling `'means in-rthelregu- 'latorexposed tofsaid source.- forffmaintainingvthe fpotential: of. said source atV a. normal/operating pressure, Vmea-ns Amounting apart lof lsaidpressure controlling-fmeans-Aradially of theregulator'forresponse to'centriugal-force, a spring acting in assistance .tov the-centrifugal force tending -to Yin- 1l5 crease the pressure above. said normal-operating pressure, and pressure loadf control fmeanscwith -passage means connecting-it with apressure fconduit responding tothe' potential of said pressure r source to meet the requirements oi operation'of 'directedbyfthefgovernor.

7 The-:combination set forth in :claim (iu/heren inthe pressureloadingcontrolA meansiincludesA a fluidpressurel feed-back" fromn one roi said'conlduits@ and aslock-out svalve responding. to-` apre- .determinedpotential of the feed-banali from -said .conduit -ior effecting a den-nite lincrementzf-Iof pressure potential f in saidV pressuresource rati' a 4.predetermined value ofthefpressurerequired for operation of .said-duid actuator` vmeans vwhenever isaid. pressure,` loading` control. means is vexposedto thedirected pressure.

.8,..A. .propeller control. mechanism `for- .use` .with an 'l hydraulically adjustable. propeller. having .f lsaid'fluidpressure.conduitsee .luid.actuated.means requiring.normalpressure .potential for. eifectingadjustment of blade-pitch .toward oneend ofthe .pitchranga.andfrequiring ,an increase oi..pressurelpotential ofthe normal .pressure potential forefecting adffustmentofathe theepposite` .end-.ot thepitch range, comprising., a. rotatable..regulatonfmeans in the regulator, providing. a sourceof uid..pres

,. .sure,. a, pair .oi fluid pressure conduits in .the

regulator.. for supplying directed. fluid'pressure to .45 .the fluidactuated means, afgovernor .valve inthe regulator havingeontrol .ports @openingsinto A,said

' conduits for-selectively.'directing theapplication of said `fluid pressure .to oneonthe othenfof. said "conduits, apressure. control valvein the regula- 50 tor `opening into said. pressure supply passage Vfor effecting 'predetermined .pressuren potentials. in

.the pressure source vin..accordance Withthe. de-

mands of said iiuid actuated means, saidv pressure .control Valve including a port andplungermeans LBS-.responding to the source pressure for reducing .to

a normal operatingT pressure of uid in said .pressure source. and Valsoincluding a secondary. piston' area with passage means connecting it with a pressure conduit responsive to governor di- C rected pressure for increasing the pressure potenltial" to" the maximum required under `extreme flight conditions'the pressure increasing means fincluding afspring biasing theplunger to close i said port,*said plunger having anlareaexposed'to G5-'pressure.directed .to one of the 'conduits anda f fl'ockout valveI responding to. a predeterminedin- Lc-rementof the directed pressure for `opposing the decreasing -normaloperating pressure.

. 9... A propeller. tcontrolmechanism for` use with .70 an hydraulically adjustable propeller-having f. fluid .actuated means requiring .normalffpressure potential. .for =e1ecting=- adjustment .of :blade -pitch .tow-ard oneend. of .thepitch range,...and requiring ,ani increase: `of ,pressure-potential oi.-..the:` Vnoni-nal 7d ...pressurefpotential for-effecting. adjustment Lof- .the

Y tor opening into said mands of blade pitch toward the opposite end of the pitch range, comprising, a rotatable regulator, means in the regulator providing a source of fluid pressure, a pair of iluid pressure conduits in the regulator for supplying directed fluid pressure to the iluid actuated means, a governor valve in the regulator having control ports opening into said conduits for selectively directing the application of said uid pressure to one or the other of said conduits, a pressure control valve in the regulapressure supply passage for effecting predetermined pressure potentials in the pressure source in accordance with the desaid fluid actuated means, said pressure control valve including a port and plunger means responding to the source pressure for reducing to a normal operating pressure of fluid in said pressure source and also including a secondary piston area with passage means connecting it with a pressure conduit responsive to governor directed pressure for increasing the pressure potential to the maximum required under extreme iiight conditions, the pressure increasing means includes a lock-out valve having an area exposed to the pressure directed to one of the conduits by the governor valve, and operable upon a predetermined potential of directed pressure to negative the reduction to normal operating pressure.

10, A propeller adjusting mechanism of the character described for use with an hydraulically adjustable propeller having provision within its hub for adjusting the pitch of its blades upon the application of fluid pressure thereto within a Wide range of positive pitch'positions and into a position of negative pitch, comprising an hydraulic regulator rotatable with the hub and providing a source of fluid pressure, a pair of control ports for supplying directed fluid pressure to the pitch adjusting provisions, a governor having control ports opening into said conduits for directing the application of pressure from said source to one or another of said control ports, and a pressure control unit opening into said pressure supply passage for regulating the pressure potential of said source in accordance with the demands of the pitch adjusting provisions said pressure control unit including an escape port and piston valve disposed radially of the regulator to be responsive to centrifugal force to close said escape'port, spring means arranged to assist centrifugal port, spring means arranged to assist centrifugal force in closing said escape port, a primary piston area continually exposed to the source of uid pressure tending to open said escape port, and a secondary piston area, with passage meansY connecting `it with a pressure conduit opposing said primary piston area and responsive to the pressure directed to one of the control ports for closing said escape port.

1l. The combination set forth in claim 10 wherein, the pressure control unit includes a lock-out valve operating in response to pressure directed to one of theecontrol ports for exposing said secondary area to a selected value of directed pressure at said control port, thereby stepping up to a predetermined increment, the pressure potential of said source when the governor directs pressure to a selected one of the control ports.

12. The combination set forth in claim wherein the pressure control unit includes a fluid passage connecting said secondary area with'the control port for negative pitch adjustment for variably increasing the pressure potential of said source directed to the pitch adjusting provisions for negative pitch.

13. In a propeller control mechanism for use wtih an hydraulically adjustable propeller having provisions for eiecting increase and decrease adjustment of the pitch of the propeller blades upon the application of fluid pressure thereto, a rotatable regulator providing a source of uid pressure, a governor Valve having a supply port constantly open to the source of fluid pressure and two control ports selectively connected to the source of fluid pressure in response to variation in speed of propeller rotation, a pressure control valve rotatable with the regulator opening to said fluid pressure source and having a primary area exposed to the source pressure at the said supply port for limiting the pressure of said source to a selected normal value, and having a secondary piston area with'a uid connection between it and both of the control ports to remove the limit on pressure of normal value when the governor valve selectively connects the pressure source with the respective control port.

14. A propeller control mechanism of the character described for use with an hydraulically adjustable propeller having a hub and a plurality of blade sockets, with uid actuated means for effecting adjustment of the pitch of the blades, comprising, means providing a source of uid pressure, a pair of fluid pressure conduits for supplying directed iluid pressure to the fluid actuated means, a governor valve having control ports opening into said conduits responsive to the speed 'of rotation of the propeller for .directing the application of said pressure uid to one or the other of said conduits, and pressure controlling means exposed to said source for maintaining the potential of said source at a normal operating pressure, said pressure controlling means including a housing having a longitudinal bore open at all times to the source potential` a porting sleeve having a bore of lesser diameter secured in one end of the housing bore, and having ports opening from the lesser diameter bore to the exterior of the housing, a plunger movable lengthwise of the housing bore and having a valving piston slidable in the bore of the sleeve, spring means urging the plunger toward one end of the housing bore so that the piston of the plunger closes communication between the bore of the housing and the ports of the sleeve, and means for applying fluid pressure to the piston in aiding relation to spring means.

15. A propeller control mechanism for use with an hydraulically adjustable propeller having iiuid actuated means for elfecting pitch adjustment of propeller blades, comprising, a pump providing a source of fluid pressure, a pair of control conduits for supplying directed fluid pressure to the iluid actuated means for increasing and for ,decreasing blade pitch, a governor valve having a and having control ports opening into said conduits operable to connect it to either of the control conduit, a plate rotatable with the propeller and providing a fluid pressure line connecting the fluid pressure source with the pressure supply port of the governorV valve, and a variable pressure control valve carried by the plate, and opening into said pressure supply passage for regulating the potential of directed fluid pressure to meet the requirements of the fluid actuated means, said pressure control valve comprising a cylindrical chamber open at all times to the source of uid pressure and providing a relief port, a plunger movable along the cylindrical chamber and having a piston cooperable with said relief port, means responding to source pressure on said piston tending to open said relief port, spring means acting on the plunger tending to close said relief port, and a fluid pressure feed-back from one of the control conduits to a portion of the piston area opposing the source pressure, and tending to close the relief port when the governor valve connects the said one control conduit with the pressure supply port.

16. The combination set forth in claim 15, wherein means mount the cylindrical chamber radially of the rotatable plate, and centrifugal force acting on the plunger assists the spring and the fluid pressure feed-back in closing the relief port.

17. The combination set forth in claim l5, wherein the fluid pressure feed back from one of the control conduits connects the control conduit for increase pitch adjustment with the said opposing piston area for applying a load control pressure tending to close said relief port and increase the pressure potential in the uid pressure line.

18.,A propeller control mechanism for use with an hydraulically adjustable propeller having fluid actuated means for effecting pitch adjustment of propeller blades, comprising, a pump providing a source of fluid pressure, a control passages for supplying directed fluid pressure to the fluid actuated means for increas ing and for decreasing blade pitch, a governor valve having a pressure supply port and operable to connect it to either of the control passages, a plate rotatable with the propeller and providing a fluid pressure line connecting the fluid pressure source with the pressure supply port of the governor valve, and a variable pressure control 'valve for regulatingV the potential of directed fluid pressure to meet the requirements of the fluid actuated means, said pressure control valve comprising a body having a cylindrical bore with a plunger movable therein for control of ay relief port, means mounting the body so that the cylindrical bore and plunger are radially disposed on the rotatable plate such that the plungertends to close the relief port under the urge of centrifugal force, spring means acting on theV plunger tending to assist centrifugal force i to close the relief port, said plunger having a piston face exposed to said cylindrical bore, passage means constantly connecting the fluid pressure line with said cylindrical bore whereby pump pressure is applied to said piston face of the plunger and acts in opposition to the spring force and centrifugal force and tends to open the relief port, and a fluid pressure feed-back connecting with one of the control passages for applying uid pressure against the plunger in opposition to the pump pressure on the pistonV pair of face when the governor connects the pressure supply port with said one control passage.

19. A propeller control mechanism for use with a variable load device having a fluid actuated reversible motor for increasing and decreasing the load in response to governor directed fluid pressure from a iluid vpressure source, comprising in combination, a rotatable member having a fluid pressure line connecting the pressure source with the said governor, a variable pressure con trol valve for controlling the potential of pressure in said fluid pressure line to effect a normal operating pressure suitable for governor control at no-change load conditions, and for increasing the potential of pressure in said uid pressure line to effect an increase over the normal operating pressure suitable to meet the requirements of operation of the reversible motor in changing the load, said pressure control valve providing a cylinder radially disposed of the rotatable member and traversed by source pressure in said fluid pressure line and having a reduced bore with a laterally extending relief port, a headed plunger movable along the cylinder and having a piston adapted to stop fluid ilow through the said relief port under the urge of centrifugal force, spring means acting upon the head of said plunger to assist the centrifugal force in closing said relief port, means continuously applying the source pressure of said fluid pressure line to the full area of said piston in opposition to the combined effects of said spring and centrifugal force and tending to open said relief port, the equilibriurn of centrifugal force, spring force and source pressure upon said plunger controlling fluid flow through said relief port by said piston to effect said normal operating pressure, and passage means connecting motor for applying load changing pressure directed to it upon a portion of the area of the valve piston in opposition to the source pressure upon the full area of the piston, the equilibrium of centrifugal force, spring force and directed load changing pressure on the one hand, balanced against source pressure of the fluid pressure line on the other hand, acting upon said plunger for restraint of relief port opening until the potential of pressure in the fluid pressure line increases sufliciently to satisfy the requirements of the reversible motor in changing the load.

HOWARD CARSON. RICHARD E. MOO-RE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,343,382 Martin Mar. 7, 1944 2,391,699 Haines et al Dec. 25, 1945 2,402,065 Martin June l1, 1946 with the reversiblem 

